Xylem 19 001 251 R3 Floboy VFD Pumping System - Manual (Page 22)

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pressure at the set point. This is the operation
sequence for Combo 2.
When the flow decreases, the VFD slows down to
maintain a constant discharge pressure.
Eventually as the speed decreases, a set point is
reached where the VSP is not pumping any water.
Because the VFD speed keeps dropping as the
flow decreases, the discharge pressure would
never get above the set point. In this situation, the
VSP would "idle," pump no water, and would
never turn off. To shut down the VSP, the system
initiates the "Speed Test" whenever the flow is
below a predetermined value for 15 seconds. The
program then lowers the set point by 5 PSI. If the
VFD speed falls below a predetermined value and
the pressure remains above the reduced set point
for 15 seconds, the VSP turns OFF.
MANUAL VFD OPERATION
Overview
Manual operation is selected by the system mode
control on the HMI. In manual operation, all pump
activity is controlled by the individual pump
switches. The speed of the VFD pump is
controlled by the speed slider on the main screen.
The PM Pump will run in XL mode (at full speed).
The LP Override setting enables or disables the
low-discharge pressure fault.
NOTE: Manual operation is rarely used. However,
it does allow for operation of individual pumps for
testing purposes.
Sequence of Operation (performed in
order)
All Individual Pump switches: OFF
Low Pressure Override setting: “Y” LDP
Override (Low Discharge Pressure fault
disabled). If initial system pressure is high
enough, disable Low Pressure Override
(Set to “N”).
System control mode: MANUAL
Pump 1 switch: ON
Speed Potentiometer: Press up-arrow to
increase speed, or press “Set” to allow
entry of speed directly (in %). Adjust as
required for flow rate / pressure required.
NOTE: When done, turn OFF all pump switches
and place system control switch in OFF. Return
LP Override setting to N. If the station can be run
in Automatic mode, return the system to AUTO
and turn ON all pump switches.